◦ Add a new reference datum by converting an existing simple reference datum into a compound reference feature. Add a secondary or tertiary reference datum by clicking either Secondary or Tertiary. Select a reference datum from the Compound list. Specify a material condition, if needed.

◦ Replace a reference datum with another datum. Click Primary, Secondary, or Tertiary (whichever is appropriate) in the Datum references box; then select a different datum name from the Basic or Compound list. If the datum that you want to use is not on the list, click Select to select it in the drawing.

◦ Remove a reference datum. Click Primary, Secondary, or Tertiary in the Datum references box (whichever is appropriate); then select None from the Basic or Compound list.